Determination of aqueous chlorothalonil with solid-phase microextraction and gas chromatography

Solid-phase microextraction coupled with GC-electron-capture detection was examined to analyze aqueous chlorothalonil residuals. The optimal condition s for chlorothalonil pre-concentration such as fiber polarity, temperature, salt addition, absorption time, as well as the interference were investiga ted in detail. In addition, the thermal desorption conditions in the inject or were also systematically optimized. Experimental results indicated that an extraction with a 100-mum polydimethylsiloxane fiber for 40 min under co nditions of 1250 rpm stirring rate, room temperature, and adding high conce ntration salt offered an optimal result. The thermal desorption of chloroth alonil at 240 degreesC for 3 min (including fiber regeneration) offered the best sensitive detection. A standard addition method for calibration was r ecommended to reduce the deviation from matrix interference. The proposed m ethod provided a simple and rapid analytical procedure for chlorothalonil i n water bodies with detection limits of 2.86 mug/l for distilled water, 3.0 6 mug/l for ground water, 4.77 mug/l for tap water, and 9.23 mug/l for farm water. The relative standard deviations were all below 3.0% (n = 6) beside s the farm water being below 9.2%. The calibration graph in the range of 5 to 200 mug/l is linear with very good correlation coefficient (r = 0.999), and r = 0.983 for farm water. Application was illustrated by the analysis o f water samples collected from tap water, ground water and farm water in th e southern Taichung area. (C) 2000 Elsevier Science B.V. All rights reserve d.